Gripper and method of manufacturing the gripper

ABSTRACT

The present invention is a gripper comprising a motor  12  for driving a connecting nut  126  that is translated, a gripping finger  103  having at least two sides of substantial V shape and a shared portion  103   g  for joining one ends of the two sides, and provided with the other ends of the sides, a base member  110  with a notch  110   c  for engaging the other end portion of the gripping member  103 , a holder member  145  having a groove  145   e  for engaging the base member  110  detachably and the hollow portions  145   m  and  145   h  that are penetrated, and a magnetic member  128  composed of a permanent magnet inserted into the hollow portions  145   m  and  145   h  of the holder member  145 , with one end connected to the connecting nut  126 , and the other end magnetically connected to the shared portion  103   g  of the gripping finger  103.

TECHNICAL FIELD

[0001] The present invention relates to a gripper for use in conveyingor assembling a minute part with improvements in replacement operationof a gripping finger.

BACKGROUND ART

[0002] A conventional gripper will be described below with reference toFIG. 10 as disclosed in the International Publication Number WO00/45999.In FIG. 10, the gripper 1 has a gripping finger 10 for gripping orreleasing a minute object and having three V-character pieces 10 v ofsubstantial V shape, a conversion portion 20 for converting the rotationof a motor shaft 12 a of a motor 12 into translation motion, theconversion portion 20 being connected to a shared portion 10 g of thegripping finger 10, a connection portion 30 for connecting theconversion portion 20 and the shared portion 10 g of the gripping finger10, a case portion 40 for accommodating the motor 12, the conversionportion 20 and the connection portion 30, and a fixing portion 50 forfixing a fixing pawl 10 t of the gripping finger 10 to the case portion40.

[0003] The conversion portion 20 comprises a screw axis 22 for fittingand securing the motor shaft 12 a of the motor 12 and having a malescrew 22 a around the outer circumference thereof, and a nut 26 forinserting the screw axis 22 and having a hollow portion formed with afemale screw 26 a to be mated with the male screw 22 a, in which therotation of the motor shaft 12 a of the motor 12 is converted intotranslation motion of the nut 26.

[0004] The connection portion 30 is formed with a protruding portion 26c having a tapped hole centrally at the top end of the nut 26, in whichthe shared portion 10 g of the gripping finger 10 is secured into thistapped hole by a screw 32.

[0005] The case portion 40 is formed of a cylindrical case 41 forreceiving the motor 12 and a part of the screw axis 22, a lid 43 forclosing a right end face of the case 41, and a holder member 45 engagedwith a left end face of the case 41, in which the holder member 45 islike a barrel having a through hole, with a substantially trapezoidalshape in cross section, and has a female screw 45 b on the outer face ofa hollow portion 45 a at the top end.

[0006] The fixing portion 50 is formed with a male screw for mating withthe female screw 45 b of the holder member 45 on an externalcircumferential face of a cylindrical presser ring 53. The fixing pawl10 t of the gripping finger 10 abuts onto the hollow portion 45 a of theholder member 45, and the fixing portion 50 is securely pressed by thepresser ring 53.

[0007] Referring to FIG. 10, the operation of the gripper as constitutedabove will be described below. First of all, the motor 12 is powered on,and then the motor shaft 12 a of the motor 12 is rotated, so that thisrotation is transmitted via the screw axis 22 to the nut 26 to move thenut 26 in a right direction as indicated in FIG. 10.

[0008] Along with this, the shared portion 10 g of the gripping finger10 is forcibly displaced by the same amount of displacement in the samedirection, and the gripping finger 10 is subjected to a bending moment,so that the V-character pieces are bent at the top end portion in thedirection coming closer to each other and closed to grip an object.

[0009] On the contrary, if the rotation of the motor 12 is reversed,with this rotation, the nut 26 is translated via the screw axis 22 in areverse direction, and the shared portion 10 g of the gripping finger 10is also translated by the same amount of displacement in the consistentmanner, so that the top end portions of the gripping finger 10 releasethe object.

[0010] However, if the gripping object of the gripping finger 10 isspherical, the gripping finger 10 maybe composed of three fingers asabove described, but if the object is like a square pole, the grippingfinger must be composed of two fingers (not shown) to grip the objectappropriately. Also, the gripping finger 10 must be exchanged due toexpiration of life, if a predetermined number of operation times isexceeded.

[0011] Such an exchange is perform in such a way that the screw 32 isfirstly turned by a screwdriver (not shown) to release engagement of theprotruding portion 26 c of the nut 26 into the tapped hole, and then thepresser ring 53 is turned by a spanner (not shown) to unscrew the holdermember 45 from the female screw 45 b, thereby detaching the grippingfinger 10.

[0012] In order to attach the gripping finger 10 on the holder member45, the screw 32 is tightened into the tapped hole of the protrudingportion 26 c by the screwdriver, the presser ring 53 is turned by thespanner and mated with the female screw 45 b of the holder member 45.Thus, there was a problem that the exchange operation of the grippingmember 10 was troublesome.

[0013] In addition, in the case where the gripper 1 is employed for anend effector of a robot, and particularly is attached verticallydownward at the top end portion of a scalar robot to be actuatedhorizontally, the gripper 1 can not be disposed sideways or upward,resulting in a problem that the exchange operation of the grippingfinger 10 alone was troublesome.

[0014] This invention is aimed at providing a gripper and itsmanufacturing method in which a gripping member is easily attached.

SUMMARY OF THE INVENTION

[0015] A gripper according to a first invention comprises an actuatorfor actuating a movement portion which translates, a gripping memberhaving at least two sides of substantial V shape, a shared portion forjoining one ends of said two sides, and the other ends of said sides, aholder member having a base member including a first engagement portionfor engaging the other ends of said gripping member thereto, a secondengagement portion for engaging said base member detachably thereto, anda hollow portion, which is penetrated, and a magnetic member made of apermanent magnet, the magnetic member one end of which is connected toone end of said movement portion, the magnetic member the other end ofwhich is magnetically connected to the shared portion of said grippingmember, the magnetic member inserted into said hollow portion of saidholder member.

[0016] With this constitution of the gripper, the other end portion ofthe gripping member is engaged with the first engagement portion of thebase member, the base member is engaged with the second engagementportion of the holder member, and the shared portion of the grippingmember is magnetically connected to the other end of the magneticmember, whereby the gripping member can be engaged with the base member,and the base member attached to the holder member in simple manner.

[0017] Further, the base member attached to the holder member isdisengaged from the second engagement portion of the holder member, andthe shared portion of the gripping member is removed from the other endof the magnetic member by pulling it with a stronger force than amagnetic adsorption of the magnetic member. Accordingly, there is theeffect that the base member having the gripping member can be easilyremoved from the holder member.

[0018] A gripper according to a second invention comprises an actuatorfor actuating a movement portion which translates, a gripping memberhaving at least two sides of substantial V shape, a shared portion forjoining one ends of said two sides, and the other ends of said sides, abase member having a bore punched in the central portion thereof, anengagement portion for engaging an end portion of said gripping memberthereto, and at least two protrusion pieces around outer circumference,a holder member having at least two grooves for engaging said protrusionpieces of said base member detachably therewith, and a hollow portion,which is penetrated, a magnetic member made of a permanent magnet, themagnetic member inserted into said hollow portion of said holder member,the magnetic member one end of which is connected to said movementportion, and a connection member one end of which is adsorbedmagnetically to the other end of said magnetic member, the connectionmember the other end of which is connected to the shared portion of saidgripping member, the connection member inserted into said hollow portionof said holder member.

[0019] With this constitution of the gripper, the end portion of thegripping member is engaged with the engagement portion of the basemember, the protrusion piece of the base member is engaged with thegroove of the holder member, and the shared portion of the grippingmember is connected to the other end of the connection member, wherebythe gripping member and the base member are attached to the connectionmember and the holder member, respectively.

[0020] The protrusion piece of the base member is removed from thegroove of the holder member, and the shared portion of the grippingmember is pulled to detach one end of the connection member from theother end of the magnetic member, whereby the gripping member and thebase member are removed from the connection member and the holdermember, respectively. Accordingly, there is the effect that the grippingmember and the base member can be easily removed from the connectionmember and the holder member, respectively.

[0021] For example, if the protrusion piece of the base member isengaged in the groove provided on the side face of the cylindricalmember having the hollow portion into which the gripping member can beinserted in a state where the base member is attached to the holdermember, the protrusion piece of the base member is easily removed fromthe groove of the holder member.

[0022] The gripper according to a third invention is characterized inthat a first slit is defined at the other end portion of said grippingmember.

[0023] With the constitution of the gripper, there is the effect that ifthe operator depresses an end portion of the gripping member, forexample, the end portion is compressed owing to a spring action, and canbe easily engaged with the engagement portion of the base member.

[0024] The gripper according to a fourth invention is characterized inthat said connection member has a tapped hole at the other end portionthereof, and the screw member is inserted into a bore of the sharedportion of said gripping member and is tightened into the tapped hole ofsaid connection member.

[0025] With the constitution of the gripper, there is the effect thatthe shared portion of the gripping member can be simply attached to ordetached from the connection member by means of the screw member.

[0026] The gripper according to a fifth invention is characterized inthat said screw member is cylindrical, and further comprises a headportion formed a minus signal shaped or plus signal shaped groove, ascrew portion tightened into the tapped hole of said connection member,and a screw preventing portion having a diameter larger than said screwportion and smaller than said head portion and having a length greaterthan the thickness of said shared portion of said gripping member, saidscrew preventing portion provided between said head portion and saidscrew portion.

[0027] With the constitution of the gripper, when the screw member isinserted into the bore of the gripping member, and tightened into thetapped hole of the connection member by a screwdriver, for example, thescrew preventing portion prevents the threaded portion of the screwmember from proceeding. Accordingly, there is the effect that thegripping member is kept from being deformed due to tightening the screwmember beyond the tolerance.

[0028] The gripper according to a sixth invention is characterized inthat said protrusion pieces of said base member define second slits.

[0029] With the constitution of the gripper, when the protrusion pieceof the base member with the gripping member is inserted into the grooveof the holder member, the protrusion piece acts as a compression springowing to the second slit provided in the base member.

[0030] Accordingly, there is the effect that the protrusion piece of thebase member with the gripping member is easily inserted into the grooveof the holder member.

[0031] The gripper according to a seventh invention is characterized inthat said shared portion of said gripping member has a slip-offprevention piece having a larger diameter than the diameter of the boreof said base member.

[0032] With the constitution of the gripper, when the base member ispulled out of the holder member, the slip-off prevention piece of thegripping member abuts against an upper portion of the innercircumferential face of the base member at a predetermined displacement,even though the shared portion of the base member is pulled. Thus, thereis the effect that the shared portion of the gripping member isrestrained in the amount of movement, thereby preventing the sides ofthe gripping member from being contacted and pressed against each other,and being deformed.

[0033] Also, there is the same effect when the gripping member is pulledand detached, because the slip-off prevention piece of the grippingmember abuts against an upper portion of the inner circumferential faceof the base member

[0034] A method for manufacturing the gripper according to an eighthinvention includes the steps of engaging the protrusion pieces of saidbase member with a engagement bore of said holder member by pressingside surfaces of the protrusion pieces of said base member with a firstgroove provided on a side face portion of a cylindrical member having ahollow portion into which said gripping member can be inserted.

[0035] Accordingly, the protrusion piece of the base member can besimply engaged into the engagement hole of the holder member, wherebythere is the effect that the base member is easily attached on theholder member.

BRIEF DESCRIPTION OF DRAWINGS

[0036]FIG. 1 is a front cross-sectional view showing the constitution ofa gripper.

[0037]FIG. 2 is a perspective view of a finger unit as shown in FIG. 1.

[0038]FIG. 3 is a plan view showing a state where a gripping finger ofFIG. 1 is expanded.

[0039]FIG. 4 is a front cross-sectional view showing the finger unit anda part of a connection portion as shown in FIG. 1.

[0040]FIG. 5 is a plan view showing a base member for fixing an endportion of the gripping finger of FIG. 1.

[0041]FIG. 6A is a plan view of a connecting nut as shown in FIG. 1, andFIG. 6B is a front cross-sectional view of the connecting nut, takenalong the arrow b-b in FIG. 6A.

[0042]FIG. 7 is a front view of a center screw as shown in FIG. 1.

[0043]FIG. 8 is a front cross-sectional view of a holder member as shownin FIG. 1.

[0044]FIG. 9 is an explanatory view showing an adjuster that is anassembly jig.

[0045]FIG. 10 is a front cross-sectional view showing the conventionalgripper.

BEST MODE FOR CARRYING OUT THE INVENTION

[0046] The preferred embodiments of the present invention will bedescribed below.

[0047] Embodiment 1

[0048] Referring to FIGS. 1 to 8, an embodiment 1 of this invention willbe described below. FIG. 1 is a front cross-sectional view showing theconstitution of a gripper. FIG. 2 is a perspective view of a fingerunit. FIG. 3 is a plan view showing a state where a gripping finger isexpanded. FIG. 4 is a front cross-sectional view showing the finger unitand a part of a connection portion. FIG. 5 is a plan view showing a basemember for fixing an end portion of the gripping finger. FIG. 6A is aplan view of a connecting nut. FIG. 6B is a front cross-sectional viewof the connecting nut taken along an arrow b-b in FIG. 6A. FIG. 7 is afront view of a center screw. FIG. 8 is a front cross-sectional view ofa holder member.

[0049] In FIG. 1, the same or like parts are designated by the samenumerals as in FIG. 10. The description of those parts is omitted.

[0050] In FIGS. 1 to 8, a gripper 100 has a finger unit 101, a motor 12as a actuator connected to a shared portion 103 g of a gripping finger103 and having a shaft 12 a for translating the shared portion 103 g, aconversion portion 120 for converting the rotation of the shaft 12 a ofthe motor 12 into translation motion, a connection portion 130 connectedto the conversion portion 120 and the shared portion 103 g of thegripping finger 103, and a case portion 140 for accommodating the motor12, the conversion portion 120 and the connection portion 130 and fixingthe finger unit 101.

[0051] The finger unit 101 has the gripping finger 103 as a grippingmember and a base member 110, as shown in FIG. 2. the gripping finger103 has two V-character pieces 103 v of substantial V shape that areopened or closed when the top end portions are widened by pulling orrestoring one end in accordance with a translation displacement to gripa minute object.

[0052] The gripping finger 103 expanded as shown in FIG. 3 issymmetrical with respect to a dotted line O, and is bent downward on thepaper along a broken line L, bent upward on the paper along a brokenline M, and bent downward on the paper along a broken line N to form thegripping finger 103 as shown in FIG. 4. The gripping finger 103 has theshared portion 103 g in the central portion, each leg portion 103 f ofthe gripping finger 103 being formed with a slit (first slit) 103 s inthe center and a cut-away end portion 103 t on either outer side.

[0053] The shared portion 103 g of the gripping finger 103 is formedwith a slip-off prevention piece 103 n having a larger diameter than thediameter of a bore 110 e of the base member 110 and with a bore 103 epunched in the central portion.

[0054] The base member 110 is like a plain washer, and has the bore 110e punched in the center and two protrusion pieces 110 t provided aroundthe outer circumference, as shown in FIG. 5. The base member 110 isprovided with two notches 110 c as a first engagement portion that areengaged by holding the leg portions 103 f of the finger 103, as shown inFIG. 5. The protrusion piece 110 t is provided with a slit 110 s (secondslit) and formed with a circular slit 110 g continuous to the slit 110 sand extending to a ring portion of the base member 110.

[0055] The width of the slits 110 s, 110 g is formed in such an extentthat if the protrusion piece 110 t is pressed by holding it from sidefaces thereof, whereby the protrusion piece 110 t is compressed due to aspring force, and the protrusion piece 110 t is inserted into a groove145 e of the holder member 145 as will be described later and releasedholding, the protrusion piece 110 t can be restored due to a springforce and engaged in the groove 145 e.

[0056] The circular slit 110 g may not be needed depending on themagnitude of spring force.

[0057] The notch 110 c of the base member 110 has a substantial T shapeas seen in a plan view, and is wider in depth than an opening. The widthof the notch 110 c in depth is formed slightly smaller than the width ofan end portion 103 t of the gripping finger 103 at the top end. Thereby,the end portion 103 t is inserted into the notch 110 c by carrying bothsides of the leg portion 103 f of the gripping finger 103 and abuttedagainst the depth portion of the notch 110 c, and then the leg portion103 f is released to engage the end portion 103 t with the notch 110 c.In this manner, the finger unit 101 is formed.

[0058] The conversion portion 120 has a moving nut 126 as a movementportion that is mated with the male screw 22 a of the screw axis 22 andhas a female screw 126 a on the outer face of a hollow portion formed bycutting the rear end, in which the rotation of the shaft 12 a of themotor 12 is converted into a translation displacement of the moving nut126.

[0059] The moving nut 126 has a rectangular outer shape to preventrotation and is formed with a cylindrical hollow portion 126 e at thefront end.

[0060] The connection portion 130 has a cylindrical magnet 128 as acylindrical magnetic member made of rare earth magnet, in which thecylindrical magnet 128 has an outer diameter slightly smaller than thebore diameter of the hollow portion 126 e in the moving nut 126, withone end portion being inserted into the hollow portion 126 e and fixedby adhesives, a connecting nut 132 as a connection member made ofmagnetic substance such as iron steel that is magnetically adsorbed andfixed on the other end face of the cylindrical magnet 128, and a centerscrew 134 inserted into the bore 103 e of the shared portion 103 g inthe gripping finger 103 and screwed into the tapped hole 132 e (see FIG.6) of the connecting nut 132.

[0061] In the case where the moving nut 126 is made of magneticsubstance, it is not required that one end portion of the cylindricalmagnet 128 is fixed to the hollow portion 126 e of the moving nut 126 byadhesives. Because it is fixed by adsorption due to a magnetic suctionforce of the cylindrical magnet 128.

[0062] The connecting nut 132 is formed like an inverse T shape in crosssection and is provided with a cylindrical portion 132 a and aninterposing portion 132 d having two flat interposing faces 132 copposed to each other to be easily turned by the spanner, as shown inFIG. 6.

[0063] The center screw 134 as the screw member is provided with a headportion 134 a having a minus groove 134 c, a screw portion 134 d matedinto the tapped hole 132 e of the connecting nut 132, and a cylindricalscrew preventing portion 134 f provided between the head portion 134 aand the screw portion 134 d, the screw preventing portion 134 f having alarger diameter than the screw portion 134 d and having a greater lengththan the thickness of gripping finger 101 at the end, as shown in FIG.7.

[0064] The screw preventing portion 134 f is formed to be slightlysmaller than the diameter of the bore 103 e in the gripping finger 103.This is because the screw preventing portion 134 f is inserted into thebore 103 e of the gripping member 103, and is movable within the bore103 e.

[0065] The groove 134 c of the center screw 134 may be plus.

[0066] The case portion 140 is formed of a lid 43, and a holder member145 engaged with a left end face of the case 41 and holding the fingerunit 101 detachably.

[0067] The holder member 145 has formed a top end hollow portion 145 mfor receiving the cylindrical magnet 128 and the center screw 134 in thecentral portion, which contains the connection portion 130 and is formedlike a barrel with substantially trapezoidal shape in cross section, anda rear end hollow portion 145 h for receiving the moving nut 126, asshown in FIGS. 1 and 8.

[0068] The holder member 145 is provided, at the top end portion, with afixing portion 145 f, which is formed to be hollow and cylindrical withsubstantially concave shape in cross section and fixing the base member110 of the finger unit 101. The fixing portion 145 f is provided withtwo grooves 145 e as the second engagement portion, into which theprotrusion piece 110 t of the base member 110 is inserted and fitted.

[0069] In a state where the protrusion piece 110 t is fitted into thegroove 145 e, a top end of the protrusion piece 110 t is slightlyprotruded out of the outer circumference of the holder member 145, asshown in FIG. 1.

[0070] The gripper 100 as constituted above can perform thesubstantially same operation as the conventional gripper.

[0071] The assembly of the gripper as constituted above will bedescribed below with reference to FIGS. 1 to 9.

[0072] Constitution of Assembly Jig

[0073] Referring to FIG. 9, an assembly jig will be described below.FIG. 9 is a front cross-sectional view (A), a right side view (B) and aplan view (C) of an adjuster for attaching the finger unit to the fingerholder.

[0074] In FIG. 9, the adjuster 200 is a cylindrical member having a bore200 e, having two protruding portions 200 b and 200 d on the upper andlower sides at the ends 200 a and 200 c, in which the protrudingportions 200 b and 200 d are provided with the grooves 200 i and 200 hfor interposing two protrusion pieces 110 t of the base member 110 inthe finger unit 101.

[0075] A groove 200 h has a slightly smaller width than the protrusionpiece 110 t of the base member 110, and is formed corresponding to theposition of the protrusion piece 110 t. A groove 200 i is formed to be aslightly smaller width than the groove 200 h.

[0076] Attaching or Detaching the Finger Unit 101

[0077] An operation of attaching or detaching the finger unit 101 to orfrom the holder member 145 using the adjuster 200 will be describedbelow.

[0078] First of all, when the finger unit 101, the connecting nut 132and the center screw 134 are not attached in FIG. 1, and when the fingerunit 101 is in a state of FIG. 2, the screw portion 134 d of the centerscrew 134 is passed through the bore 103 e of the shared portion 103 gin the gripping finger 103 and mated into the tapped hole 132 e of theconnecting nut 132, as shown in FIG. 3.

[0079] While the bore 200 e of the adjuster 200 is being put on thegripping finger 103 from the above, the groove 200 h of the adjuster 200is slidingly pressed on the side face of the protrusion piece 110 t ofthe base member 110. Since a pressing force is exerted to interpose theprotrusion piece 110 t, the protrusion pieces 110 t are elasticallydeformed toward each other under the pressure of the adjuster 200,thereby narrowing the gap between the slits 110 s, so that the width ofthe protrusion piece 110 t is equal to that of the groove 200 h of theadjuster 200.

[0080] And the protrusion piece 110 t of the base member 110 is engagedin the groove 200 h. In this engaged state, the protrusion piece 110 tis fitted into the groove 145 e of the holder member 145, and interposedunder a predetermined compression force, thereby attaching the fingerunit 101 on the holder member 145. Since the compression force of thegroove 200 h of the adjuster 200 is released by fitting the protrusionpiece 110 t into the groove 145 e of the holder member 145, the groove200 h of the adjuster 200 is easily detached from the protrusion piece110 t of the base member 110. At the same time, an end face of theconnecting nut 132 is magnetically adsorbed onto an end face of thecylindrical magnet 128, thereby completing the gripper 100 as shown inFIG. 1.

[0081] On the other hand, in the gripper 100 as shown in FIG. 1, theprotrusion piece 110 t is subjected to a pressure with one end 200 c ofthe adjuster 200 in contact with the finger unit 101, and furthercompressed, while sliding it on the side face of the protrusion piece110 t of the base member 110, to be engaged in the groove 200 i of theadjuster 200, whereby the protrusion piece 110 t is disengaged from thegroove 145 e of the holder member 145.

[0082] If the adjuster 200 is lifted, the center screw 134 and theconnecting nut 132 connected to the finger unit 101 are lifted at thesame time, and an end face of the connecting nut 132 is released fromthe magnetic adsorption with an upper face of the cylindrical magnet128, whereby the finger unit 101, the center screw 134 and theconnecting nut 132 can be easily removed from a main body of the gripper100.

[0083] In lifting the finger unit 101 by means of the adjuster. 200, theslip-off prevention piece 103 n of the finger 103 abuts against thesurface of the base member 110 to act as a stopper. Accordingly, theshared portion 103 g of the finger 103 is restrained in the amount ofmovement, thereby preventing the V-character sides 103 v of the grippingfinger 103 from being contacted and pressed to deform the V-charactersides 103 v.

[0084] The members described in this specification are onlyillustrative, and the invention is not limited to those members.

INDUSTRIAL APPLICABILITY

[0085] As described above, the gripper of the present invention issuitable for exchanging the gripping member simply.

1. A gripper comprising: an actuator for actuating a movement portionwhich translates; a gripping member having at least two sides ofsubstantial V shape, a shared portion for joining one ends of said twosides, and the other ends of said sides; a holder member having a basemember including a first engagement portion for engaging the other endsof said gripping member thereto, a second engagement portion forengaging said base member detachably thereto, and a hollow portion,which is penetrated; and a magnetic member made of a permanent magnet,the magnetic member one end of which is connected to one end of saidmovement portion, the magnetic member the other end of which ismagnetically connected to the shared portion of said gripping member,the magnetic member inserted into said hollow portion of said holdermember.
 2. A gripper comprising: an actuator for actuating a movementportion which translates; a gripping member having at least two sides ofsubstantial V shape, a shared portion for joining one ends of said twosides, and the other ends of said sides; a base member having a borepunched in the central portion thereof, an engagement portion forengaging an end portion of said gripping member thereto, and at leasttwo protrusion pieces around outer circumference; a holder member havingat least two grooves for engaging said protrusion pieces of said basemember detachably therewith, and a hollow portion, which is penetrated;a magnetic member made of a permanent magnet, the magnetic memberinserted into said hollow portion of said holder member, the magneticmember one end of which is connected to said movement portion; and aconnection member one end of which is adsorbed magnetically to the otherend of said magnetic member, the connection member the other end ofwhich is connected to the shared portion of said gripping member, theconnection member inserted into said hollow portion of said holdermember.
 3. The gripper according to claim 1 or 2, wherein a first slitis defined at the other end portion of said gripping member.
 4. Thegripper according to claim 2, further comprising a screw member, whereinsaid connection member has a tapped hole at the other end portionthereof; and wherein the screw member is inserted into a bore of theshared portion of said gripping member and is tightened into the tappedhole of said connection member.
 5. The gripper according to claim 4,wherein said screw member is cylindrical, and further comprises a headportion formed a minus signal shaped or plus signal shaped groove, ascrew portion tightened into the tapped hole of said connection member,and a screw preventing portion having a diameter larger than said screwportion and smaller than said head portion and having a length greaterthan the thickness of said shared portion of said gripping member, saidscrew preventing portion provided between said head portion and saidscrew portion.
 6. The gripper according to claim 2, wherein saidprotrusion pieces of said base member define second slits.
 7. Thegripper according to claim 2, wherein said shared portion of saidgripping member has a slip-off prevention piece having a larger diameterthan the diameter of the bore of said base member.
 8. A method formanufacturing the gripper according to claim 2, comprising the steps ofengaging the protrusion pieces of said base member with a engagementbore of said holder member by pressing side surfaces of the protrusionpieces of said base member with a first groove provided on a side faceportion of a cylindrical member having a hollow portion into which saidgripping member can be inserted.